Combined omni- and directional- communications in high-frequency wireless networks

ABSTRACT

In a wireless communication network, specific portions of the communication may combine directional transmission with omnidirectional reception. In particular, sector-level directional transmission may be established through sector sweeps, followed by antenna training for more directionality. In some embodiments, collisions during the exchange may be reduced by having different network devices use different sub-channels or different time slots. In some embodiments, each network may restrict its network communications to a single sub-channel that is different than the sub-channels used by adjacent networks.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is related to U.S. provisional patent application Ser.No. 61/035,480, filed Mar. 11, 2008, and claims priority to that filingdate for all applicable subject matter.

BACKGROUND

High-frequency wireless communications, such as in the 60 GHz WirelessPersonal Area Networks currently being developed, tend to be limited toshort-range communications because of the level of absorption of thesignals by oxygen in the air. For this and other reasons, thistechnology is most suitable for personal area networks that havemultiple devices communicating with each other within a small area. Inmany applications, this will lead to a dense operating environment, inwhich multiple such networks that are adjacent and overlapping will tendto interfere with each other. To reduce the level of this interference,communications tend to be directional and prescheduled. But somecommunications, by their very nature, need to be omnidirectional andunscheduled. Choosing one or the other usually requires trading off theadvantages and disadvantages of each.

BRIEF DESCRIPTION OF THE DRAWINGS

Some embodiments of the invention may be understood by referring to thefollowing description and accompanying drawings that are used toillustrate embodiments of the invention. In the drawings:

FIG. 1 shows multiple wireless networks, according to an embodiment ofthe invention.

FIG. 2 shows sectorized directional transmission from each of twonetwork devices, according to an embodiment of the invention.

FIG. 3 shows a frame structure, according to an embodiment of theinvention.

FIG. 4 shows contents of the sector sweep device discovery period ofFIG. 3, according to an embodiment of the invention.

FIG. 5 shows contents of the contention period of FIG. 3, according toan embodiment of the invention.

FIG. 6 shows a flow diagram of a method of achieving directionalcommunications by a wireless network controller, according to anembodiment of the invention.

FIG. 7 shows a flow diagram of a method of achieving directionalcommunications by a non-controller wireless device in a network,according to an embodiment of the invention.

DETAILED DESCRIPTION

In the following description, numerous specific details are set forth.However, it is understood that embodiments of the invention may bepracticed without these specific details. In other instances, well-knowncircuits, structures and techniques have not been shown in detail inorder not to obscure an understanding of this description.

References to “one embodiment”, “an embodiment”, “example embodiment”,“various embodiments”, etc., indicate that the embodiment(s) of theinvention so described may include particular features, structures, orcharacteristics, but not every embodiment necessarily includes theparticular features, structures, or characteristics. Further, someembodiments may have some, all, or none of the features described forother embodiments.

In the following description and claims, the terms “coupled” and“connected,” along with their derivatives, may be used. It should beunderstood that these terms are not intended as synonyms for each other.Rather, in particular embodiments, “connected” is used to indicate thattwo or more elements are in direct physical or electrical contact witheach other. “Coupled” is used to indicate that two or more elementsco-operate or interact with each other, but they may or may not be indirect physical or electrical contact.

As used in the claims, unless otherwise specified the use of the ordinaladjectives “first”, “second”, “third”, etc., to describe a commonelement, merely indicate that different instances of like elements arebeing referred to, and are not intended to imply that the elements sodescribed must be in a given sequence, either temporally, spatially, inranking, or in any other manner.

Various embodiments of the invention may be implemented in one or anycombination of hardware, firmware, and software. The invention may alsobe implemented as instructions contained in or on a machine-readablemedium, which may be read and executed by one or more processors toenable performance of the operations described herein. Amachine-readable medium may include any mechanism for storing,transmitting, and/or receiving information in a form readable by amachine (e.g., a computer). For example, a machine-readable medium mayinclude a tangible storage medium, such as but not limited to read onlymemory (ROM); random access memory (RAM); magnetic disk storage media;optical storage media; a flash memory device, etc. A machine-readablemedium may also include a propagated signal which has been modulated toencode the instructions, such as but not limited to electromagnetic,optical, or acoustical carrier wave signals.

The term “wireless” and its derivatives may be used to describecircuits, devices, systems, methods, techniques, communicationschannels, etc., that communicate data by using modulated electromagneticradiation through a non-solid medium. The term does not imply that theassociated devices do not contain any wires, although in someembodiments they might not. Each wireless network device will compriseat least a wireless transmitter, a wireless receiver, and a processor.

In various embodiments, directional transmission may be combined withomnidirectional reception during device discovery and during bandwidthrequests to achieve high gain and reduce interference with otherdevices. For the purposes of this document, omnidirectional receptionrefers to receiving a signal with an antenna in which signals of similarstrength at the location of the antenna will be received with similarapparent strength from any part of the 360 degree coverage area of theantenna. Directional transmission refers to an antenna system with whichtransmitted signals will be stronger in a particular direction than inthe other directions. In some embodiments, each network in amulti-network environment will combine this approach with using a narrowsub-channel, different than the sub-channel used by adjacent networks,to further reduce interference between networks. In other embodiments,different sub-channels or different time slots may be used by individualmobile devices within a network during a contention period to reduce thechance of collisions during that period.

FIG. 1 shows multiple wireless networks, according to an embodiment ofthe invention. Within the context of this document, every wirelessnetwork is considered to comprise a wireless network controller and oneor more other wireless devices that are associated with the controllerand whose communications may be mostly scheduled by the controller. Forconvenience of reference within this document, each network may bereferred to as a piconet (which typically may operate at or near the 60GHz band), each network controller may be referred to as a PNC, and eachof the other network devices may be referred to as a DEV, as thatterminology is already common in piconet technology. However, the use ofthose terms in this document should not be construed as limiting theembodiments of the invention to piconets, or to devices that are labeledas PNC or DEV, unless those limitations are specifically claimed.

In the illustrated example, a first network includes a piconetcontroller PNC1, and four DEV's A, B, C, and D associated with PNC1. Thesecond network includes piconet controller PNC2, and three DEV's F, G,and H associated with PNC2. Another DEV E is currently not associatedwith either PNC, but could presumably become associated with either PNCbecause of its proximity to both PNC's.

Any or all of the wireless devices PCN1, PCN2, and A-H may contain abattery to provide operational power to the device. Also, any or all ofthe wireless devices PNC1, PNC2, and A-H may have multiple antennas fordirectional communication. Such directionality may be achieved bycombining the multiple antennas into a phased array antenna system, inwhich each antenna is substantially omnidirectional by itself, butdirectionality may be achieved by processing the separate signals to orfrom each antenna in a manner that achieves directionality for theoverall antenna array. For omnidirectional communications with a phasedarray antenna system, a single antenna may be selected for transmissionor for reception, while the other antennas in the array may be turnedoff or otherwise not used for that purpose.

For coarse directionality, the normal 360 degree coverage ofomnidirectional communications may be divided into a given number ofadjacent sectors. Each transmission may be relatively strong in a givensector, while being relatively weak in all the other sectors. Theprocessing parameters for such coarse, sector-level, directionality maybe pre-programmed into the device. For fine directionality, with itsresulting higher gain, a subsequent antenna training session between twodevices may be required. For convenience of reference, each sector maybe described in terms of the device doing the transmitting. For example,controller sectors are sectors defined by the network controller fortransmissions from the network controller, and DEV sectors are sectorsdefined by a DEV for transmissions from the DEV.

FIG. 2 shows sectorized directional transmission from each of twonetwork devices, according to an embodiment of the invention. Theexample shows eight sectors for transmissions from PNC 1 (labeled 1-8),and six sectors for transmissions from DEV A (labeled A1-A6 todistinguish them from the sectors of the PNC), but other quantities mayalso be used in either device. As an example of sectorizedtransmissions, a DEV A that lies within PNC 1's sector 3 (as shown inFIG. 2) may be able to receive a strong signal while the PNC istransmitting in sector 3, but may receive a relatively weak, or evenundetectable, signal while the PNC is transmitting in any other sector.Similarly, if PNC 1 lies within DEV A's sector A5 (as shown in FIG. 2),then PNC 1 may be able to receive a strong signal while DEV A istransmitting in sector A5, but may receive a relatively weak, or evenundetectable, signal while DEV A is transmitting in any other sector. Ifa receiving device is located near the border between two adjacentsectors of the transmitting device, it might be able to receive a usablesignal from either sector, although one would probably be stronger thanthe other.

A sector sweep transmission is a technique in which the same basicinformation is transmitted in each individual sector at separate times,until that basic information has been transmitted in all the sectors.The sectors may typically be selected in sequential order, eitherclockwise or counterclockwise, but other orders of selection may also beused. Although the same basic information is transmitted in each sectorduring a sector sweep, there may be minor differences in thatinformation. For example, the transmission may contain theidentification of the sector currently being used, so that receivingdevices will know which of the transmitter's sectors provide them withthe best signal. Timing information, if included, may also be differentfor each sector, since each is transmitted at a different time.

FIG. 3 shows a frame structure, according to an embodiment of theinvention. Although particular parts of the frame are shown in aparticular order, other embodiments may contain more, fewer, and/ordifferent parts, and the order may be different. The parts shown aregeneral in nature, and may contain additional detail not shown, such asheaders, information elements, interframe spaces, etc. In theillustrated example of FIG. 3, one or more directional beacons may betransmitted by the PNC near the beginning of the frame. This beacon maybe addressed to those devices that are already associated with the PNC.Since directional communication with these devices has already beenestablished in previous frames, the beacons may be transmitteddirectionally, using either sector directionality or finedirectionality. In some embodiments, a multicast addressing format maybe used if multiple receiving devices can be reached by the samedirectional transmission.

Next, a device discovery process may be implemented to discover newdevices that wish to join this network. Since the PNC does not know inwhich direction these potential network devices might be located, thediscovery beacon(s) should be transmitted in all horizontal directions.Rather than transmitting a discovery beacon as a single omnidirectionaltransmission, this may be accomplished with a sector sweep, bytransmitting the discovery beacon at a separate time for each sector.Each of these separate transmissions may contain the identification ofthe sector that the transmission covers. In addition to identifying newdevices for the network, the device discovery period may also be used togather information about the direction of these new devices so thatsubsequent transmissions to/from them may be directional. A moredetailed description of the contents of the sector sweep devicediscovery part is presented later.

A contention period may follow the sector sweep device discovery portionof the frame. During the contention period, DEV's may transmit to thePNC without being pre-scheduled to do so, by simply transmitting whenthe channel appears to be idle. However, if more than one DEV istransmitting at the same time, a collision may occur, causing one orboth signals to be received incorrectly by the PNC. Various techniquesmay be used to reduce, and/or recover from, the collisions that mayresult from this method. For example, each device may use one ofmultiple available sub-channels. By using different sub-channels, eachdevice's transmission may be simultaneously received by the PNC withoutinterference. In another example, the contention period may be dividedinto multiple pre-defined time slots, and each device may use aparticular time slot for its transmission. In some embodiments, thedevice will randomly select which sub-channel or time slot it will usefor transmission. Using either the sub-channel or time slot technique,it is still possible that both devices will select the same sub-channel,or the same time slot, and interference will still occur. But thechances of such interference are greatly reduced by either of thesetechniques. Of course, if a collision does occur, causing incorrectreception of one or both transmissions, any of various techniques may beused to retransmit the information.

During the contention period, the PNC and DEV's may exchange additionalinformation that can improve the directionality of subsequentcommunications between them. For example, the devices may performantenna training to achieve fine directionality during this period. Themobile devices may also each perform bandwidth requests during thisperiod to reserve one or more subsequent time periods for communicationswith the PNC during the Data Comm portion of the frame.

Following the contention period, data may be exchanged between the PNCand the various DEV's that are associated with it, following a scheduleissued by the PNC (which may be based at least partly on theaforementioned bandwidth requests in previous frames). These periods arelabeled Data Comm in the drawing. Because of the information ondirectionality that was determined earlier, all or most of thisscheduled communication may use direction transmissions and eitherdirectional or omnidirectional receptions, by both the PNC and by theDEV's.

FIG. 4 shows contents of the sector sweep device discovery period ofFIG. 3, according to an embodiment of the invention. The illustratedembodiment includes three portions, although other embodiments maycontain more or fewer than three. The first portion includes thediscovery beacon transmitted by the PNC, using the sector sweeptechnique. For example, the PNC may directionally transmit the discoverybeacon to sector 1, then directionally transmit the discovery beacon tosector 2, then sector 3, etc., until all the sectors have been covered.Each discovery beacon may also include other information, such as theidentity of the particular sector that is being covered at that time.During this portion, the PNC may use a directional transmission for eachsector. Any DEV's that are looking for a discovery beacon may useomnidirectional reception, since they won't know in advance whichdirection a beacon will come from.

Following the first portion, the second portion may be used to giveDEV's a chance to respond to the beacon. The response of a single DEV Ais shown. In a conventional system, the response would be transmittedomnidirectionally by the DEV. However, since we wish to obtaindirectional information for use with subsequent communications, theresponse may use a sector sweep approach. The DEV may transmit theresponse directionally to sector A1, then transmit the responsedirectionally to sector A2, then sector A3, etc., until all the sectorshave been covered. The sectors of the mobile device A are eachidentified with an “A” prefix before the sector number (A1 through An)to distinguish them from the sectors 1 through N that are used by thePNC. The number of sectors used by the PNC may or may not be the same asthe number of sectors used by the DEV.

The response of DEV A may contain several pieces of information, such asbut not limited to: 1) a request to become associated with the PNC, 2)the identity of the responding DEV, 3) the sector number of the DEV thatthis particular response is being transmitted to (remember, a separateresponse is transmitted for each sector), 4) the PNC sector number thatwas contained in the beacon that this DEV is responding to, 5) etc. Ifthe DEV was able to receive the discovery beacon in more than one PNCsector, the DEV may specify which of those PNC sectors it prefers(typically the sector that contained the best quality signal, asdetermined by signal strength and/or signal-to-noise ratio, though othercriteria may be used).

In the third portion of the device discovery period, labeled Mgmt Info(Management Information) in the drawing, the PNC may communicateadditional information to the DEV. Since the DEV informed the PNC duringthe second portion as to which PNC sector should be used fortransmissions to the DEV, all transmissions to the DEV during the thirdportion may be directional transmissions, using the indicated PNCsector. The information communicated to the DEV during the third portionmay include the DEV sector number that the DEV should subsequently usewhen transmitting to the PNC. If the PNC only received the response inone sector, then this is the sector that should be specified. If the PNCreceived the response in more than one sector from the DEV, then it canselect the best sector for the DEV to use, using criteria similar tothat described in the previous paragraph.

After receiving this information on sector number, the DEV maysubsequently use that sector for directional transmissions to the PNC.The PNC and DEV may also exchange other information during the thirdperiod, and may both use directional transmissions for the remainder ofthe third period. These directional transmissions may also be used forsubsequent communications between these two devices, using the sectornumbers specified during the device discovery period. However, afterantenna training has been performed later to achieve finedirectionality, the parameters for fine directionality may be usedinstead of those for the coarse sector-level directionality.

Because some network devices may sometimes be moved during operation,thus changing the optimal selection of sectors, the process for sectordetermination may sometimes need to be repeated, even though the devicediscovery process is not being invoked. In this case, sector sweeps maybe performed external to the device discovery phase. This reselection ofsectors may be triggered by any of several events, such as but notlimited to: 1) sector selection may be repeated at predeterminedintervals, 2) when the signal quality falls below a certain thresholdfor a predetermined period of time, 3) when communication is completelyinterrupted, 4) when a predetermined external event occurs, 5) etc.

FIG. 5 shows contents of the contention period of FIG. 3, according toan embodiment of the invention. The illustrated embodiment includes twoportions, although other embodiments may contain a different quantity ofportions. The first portion includes bi-directional antenna trainingsequences. By the beginning of the contention period, eachnewly-associated DEV in the network has already exchanged sectorinformation with the PNC, so coarse directional communication within thegranularity of a single sector is possible. However, for higher gain andpotentially higher data rates, fine directionality (i.e., a narrowerbeam) may be necessary. Antenna training may be required to achievethis, in which each device transmits predetermined data patterns to theother device. Using various signal processing techniques, each devicecan derive which parameters to use for transmission, and for reception,to achieve the desired narrow beam results. These two devices may thenuse these parameters in subsequent communications. If one or bothdevices is moved, new antenna training may be required to determine newparameters. Various antenna training techniques are known, and are notdiscussed here in more detail.

The second portion of the illustrated contention period may be used forbandwidth requests. In a bandwidth request, the DEV requests that aportion of time be reserved for the DEV to communicate with the PNC. ThePNC then schedules a certain time period for such communication, makingsure that it does not conflict with other time periods scheduled forother DEV's, and transmits this schedule back to the DEV. This scheduledperiod may fall within the Data Comm part of FIG. 3. Various techniquesfor scheduling dedicated periods of communication are known and are notdiscussed here in more detail.

FIG. 6 shows a flow diagram of a method of achieving directionalcommunications by a wireless network controller, according to anembodiment of the invention. In the illustrated embodiment of flowdiagram 600, at 610 the PNC transmits a discovery beacon, using thesector sweep techniques described previously to directionally transmitthe beacon at separate times in each of multiple sectors. The beacon toeach sector will include the sector number of that sector, as the sectornumbers are defined by the PNC. Note: the term “sector number”, as usedherein, includes any type of sector identifier, whether or not theidentifier is an actual number.

After performing the sector sweep, at 620 the PNC may go toomnidirectional reception to monitor for a response to the discoverybeacon from a DEV wishing to join (or rejoin) the network. If noresponse is received within the prescribed amount of time, the PNC mayexit this flow diagram at 630, and continue performing the operations itwould normally perform, operations that are not further described here.However, if a response is received, the PNC may read the contents of theresponse at 640, those contents including the responder sector number(i.e., the sector that the responding DEV was transmitting in when ittransmitted this response), and the controller sector number (i.e., thesector number that was identified in the discovery beacon that thisresponse is responding to). The network controller may then use thiscontroller sector number for subsequent directional transmissions tothis DEV.

To permit the responding DEV to associate with the network controller,at 650 the PNC may transmit various association information to the DEV.The nature of much of this information is well established and is notfurther described here. However, unlike conventional systems, the PNCmay also transmit the responder sector number that was read from theresponse. By transmitting the identity of this sector, the PNC istelling the responding DEV which sector to use for subsequentdirectional transmissions to the PNC. The association information andthe responder sector number may be transmitted directionally, using thecontroller sector number that was read from the response.

At this point, both the network controller and the DEV know which oftheir respective sectors to use for directional transmissions to eachother. However, further antenna training may be necessary to achievedirectionality that is narrower than a sector. The PNC and the DEV mayperform this antenna training at 660. Further communications betweenthem may then be performed with a narrow beam at 670, using the finedirectional parameters established during antenna training.

FIG. 7 shows a flow diagram of a method of achieving directionalcommunications by a non-controller wireless device in a network,according to an embodiment of the invention. In the illustratedembodiment of flow diagram 700, at 710 a DEV may use omnidirectionalreception techniques to receive a discovery beacon from a PNC. The DEVmay then read the controller sector number from the received beacon at720. The DEV may then respond to the beacon at 730 by transmitting arequest to associate with the PNC, using the sector sweep techniquesdescribed previously to directionally transmit the response at separatetimes in each of multiple sectors. The transmission to each sector willinclude the DEV sector number of that sector, as the sector numbers aredefined within the DEV. Subsequently, using omnidirectional receptiontechniques, at 740 the DEV may receive information from the PNCpertaining to associating with the PNC, along with the DEV sector numberto use in subsequent transmissions to the PNC

At this point, both the DEV and the PNC have the information needed toperform coarse directional transmissions at the sector level whencommunicating with each other. But to be capable of achieving finedirectional transmissions and fine directional receptions, antennatraining may be performed between the two devices at 750. After suchtraining, subsequent communications between the two devices may use theparameters for fine directional communications, as indicated at 760.

The foregoing description is intended to be illustrative and notlimiting. Variations will occur to those of skill in the art. Thosevariations are intended to be included in the various embodiments of theinvention, which are limited only by the spirit and scope of thefollowing claims.

1. A method, comprising performing operations in a first wirelessnetwork device, the operations comprising: omnidirectionally receiving adiscovery beacon including a first sector number identifying a firstsector within which the discovery beacon was transmitted by a secondwireless network device; directionally transmitting to the secondwireless network device, within a second sector, a response including asecond sector number identifying the second sector; directionallytransmitting to the second wireless network device, within a thirdsector, the response including a third sector number identifying thethird sector; and omnidirectionally receiving, from the second wirelessnetwork device, information containing a particular one of the secondand third sector numbers; and directionally transmitting additionalinformation to the second wireless network device, within the sectoridentified by the particular one of the second and third sector numbers.2. The method of claim 1, the operations further comprising performingantenna training with the second wireless network device.
 3. The methodof claim 1, wherein said transmitting the additional informationcomprises transmitting over one of multiple available sub-channels. 4.The method of claim 1, wherein said transmitting the additionalinformation comprises transmitting during one of multiple available timeslots.
 5. The method of claim 1, wherein said performing the operationscomprises performing the operations within a piconet network.
 6. Anapparatus, comprising a first wireless network device containing awireless transmitter, a wireless receiver, and a processor, the firstwireless network device to: omnidirectionally receive a discovery beaconincluding a first sector number identifying a first sector within whichthe discovery beacon was transmitted by a second wireless networkdevice; directionally transmit to the second wireless network device,within a second sector, a response including a second sector numberidentifying the second sector; directionally transmit to the secondwireless network device, within a third sector, the response including athird sector number identifying the third sector; omnidirectionallyreceive, from the second wireless network device, information containinga particular one of the second and third sector numbers; anddirectionally transmit additional information to the second wirelessnetwork device, within the sector identified by the particular one ofthe second and third sector numbers.
 7. The apparatus of claim 6,wherein the first wireless network device is to perform antenna trainingwith the second wireless network device.
 8. The apparatus of claim 6,wherein the first wireless network device is to transmit the additionalinformation over one of multiple available sub-channels.
 9. Theapparatus of claim 6, wherein the first wireless network device is totransmit the additional information during one of multiple availabletime slots.
 10. The apparatus of claim 6, wherein the first and secondwireless network devices are to operate within a piconet network. 11.The apparatus of claim 6, wherein the first wireless network devicecomprises multiple antennas in a phased array antenna system.
 12. Anarticle comprising a tangible machine-readable medium that containsinstructions, which when executed by one or more processors result inperforming operations comprising: omnidirectionally receiving adiscovery beacon including a first sector number identifying a firstsector within which the discovery beacon was transmitted by a secondwireless network device; directionally transmitting to the secondwireless network device, within a second sector, a response including asecond sector number identifying the second sector; directionallytransmitting to the second wireless network device, within a thirdsector, the response including a third sector number identifying thethird sector; omnidirectionally receiving, from the second wirelessnetwork device, information containing a particular one of the secondand third sector numbers; and directionally transmitting additionalinformation to the second wireless network device, within the sectoridentified by the particular one of the second and third sector numbers.13. The medium of claim 12, wherein the operations further compriseperforming antenna training with the second wireless network device. 14.The medium of claim 12, wherein the operation of transmitting theadditional information comprises transmitting over one of multipleavailable sub-channels.
 15. The medium of claim 12, wherein theoperation of transmitting the additional information comprisestransmitting during one of multiple time slots available for theadditional information.